This is going to be very interesting to see how the feds deal with this one in the near future. People "printing" out guns on the new 3d printers.

http://arstechnica.com/tech-policy/2013/...ver-600-rounds/

For people that don't know the lower reciever of a AR15 is the registered part and pretty soon you will be able to sit at home on your pc and just hit the print button and print out as many as you want. Still not great but these guys are getting better and better at making these receivers. I have no doubt that within a few more years this will be a major problem for our pals at the BATF.